1. Field of the Invention
The present invention relates to a method for manufacturing a quantum-dot element and, more particularly, to a method for manufacturing a photoelectric element with colloidal quantum dots, such as a light-emitting diode, a laser diode, a detector, a photonic crystal, or a magnetic thin film.
2. Description of Related Art
Recently, the hybrid of organic or inorganic materials has become the emphasis of the development in photoelectric materials. On the other hand, the nano-particulate obtained by liquid or gaseous synthesis is also the focus of the development in material technology. Although the nano-particulate as well as the composite of the nano-particulate and the organic molecule inherently has good material property, they become deteriorated when being applied to the photoelectric devices. The main problem lies in that the manufacturing process of the nano-particulate is not compatible with the vacuum process for manufacturing the photoelectric element and, therefore, the manufacturing of the photoelectric element with the nano-particulates can not be carried out in a continuous process.
Generally, the quantum dot of the quantum-dot element is formed by either vacuum process or chemical synthesis. The vacuum process further includes the Molecular Beam Epitaxy (MBE) method, the Chemical Vapor Deposition (CVD) method, and the Ultrahigh Vacuum Physical Vapor Deposition (UHVPVD) method. However, the quantum dots formed by these vacuum processes usually have too large particle sizes (usually larger than 10 nm) and too low densities. Also, the particle sizes are not uniform enough. Therefore, the quantum dots formed by the vacuum process are unsuitable for a manufacturing device with a large superficial content. As for the chemical synthesis, it can produce quantum dots with well-distributed size, which generally ranges from 1 nm to 10 nm. In addition, the quantum dots formed by the chemical synthesis have a higher density, so they can be used to manufacture devices with large superficial content. The quantum-dot layer formed by the conventional chemical synthesis is shown as FIGS. 1a to 1c. First, the particles 10 and the organic molecules 20 are mixed in an atmosphere of inert gas, which prevents the particles 10 from oxidizing. Namely, the quantum dots are dispersed in the organic solvent, as shown in FIG. 1a. Afterwards, the quantum dots in the organic solvent are deposited onto the substrate 30 by spin coating in the grove box, as shown in FIG. 1b. Subsequently, the substrate 30 is put into the vacuum evaporation chamber or the sputtering chamber for depositing a carrier transport film or an electrode 40, as shown in FIG 1c. However, the quantum dots may easily aggregate in the aforesaid process, as shown in FIG. 2c. Besides, the product is easily contaminated during the mixing or the spin coating step, and consequently suffers from quality deterioration. Moreover, the product might be damaged when it is transported between different manufacturing apparatuses. In addition to the above-mentioned method, the quantum dots may also be adsorbed onto the substrate by dipping. However, although a uniform layer of quantum dots can be formed, the solvent might easily contaminate other parts of the quantum-dot element such as the carrier transport layer or the electrode.
In order to overcome the imperfection of such a non-continuous process, the apparatus for manufacturing quantum-dot element of the present invention combines the conventional aerosol spraying process with the vacuum process. In particular, the aerosol spraying process is used for introducing the solid powders. Therefore, the organic-inorganic composite element can be manufactured in a single chamber, and the bottleneck of deterioration in material quality can be substantially improved.